/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.tsfile.read.reader.series;

import org.apache.iotdb.tsfile.file.metadata.AlignedChunkMetadata;
import org.apache.iotdb.tsfile.file.metadata.ChunkMetadata;
import org.apache.iotdb.tsfile.file.metadata.IChunkMetadata;
import org.apache.iotdb.tsfile.file.metadata.enums.TSDataType;
import org.apache.iotdb.tsfile.read.common.BatchData;
import org.apache.iotdb.tsfile.read.common.Chunk;
import org.apache.iotdb.tsfile.read.controller.IChunkLoader;
import org.apache.iotdb.tsfile.read.reader.IChunkReader;
import org.apache.iotdb.tsfile.read.reader.chunk.AlignedChunkReader;
import org.apache.iotdb.tsfile.read.reader.chunk.ChunkReader;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

/**
 * Series reader is used to query one series of one tsfile, using this reader to query the value of
 * a series with given timestamps.
 */
public class FileSeriesReaderByTimestamp {

    protected IChunkLoader chunkLoader;
    protected List<IChunkMetadata> chunkMetadataList;
    private int currentChunkIndex = 0;

    private IChunkReader chunkReader;
    private long currentTimestamp;
    private BatchData data = null; // current batch data

    /**
     * init with chunkLoader and chunkMetaDataList.
     */
    public FileSeriesReaderByTimestamp(
            IChunkLoader chunkLoader, List<IChunkMetadata> chunkMetadataList) {
        this.chunkLoader = chunkLoader;
        this.chunkMetadataList = chunkMetadataList;
        currentTimestamp = Long.MIN_VALUE;
    }

    public TSDataType getDataType() {
        return chunkMetadataList.get(0).getDataType();
    }

    /**
     * get value with time equals timestamp. If there is no such point, return null.
     */
    @SuppressWarnings("squid:S3776") // Suppress high Cognitive Complexity warning
    public Object getValueInTimestamp(long timestamp) throws IOException {
        this.currentTimestamp = timestamp;

        // first initialization, only invoked in the first time
        if (chunkReader == null) {
            if (!constructNextSatisfiedChunkReader()) {
                return null;
            }

            if (chunkReader.hasNextSatisfiedPage()) {
                data = chunkReader.nextPageData();
            } else {
                return null;
            }
        }

        while (data != null) {
            while (data.hasCurrent()) {
                if (data.currentTime() < timestamp) {
                    data.next();
                } else {
                    break;
                }
            }

            if (data.hasCurrent()) {
                if (data.currentTime() == timestamp) {
                    Object value = data.currentValue();
                    data.next();
                    return value;
                }
                return null;
            } else {
                if (chunkReader.hasNextSatisfiedPage()) {
                    data = chunkReader.nextPageData();
                } else if (!constructNextSatisfiedChunkReader()) {
                    return null;
                }
            }
        }

        return null;
    }

    /**
     * Judge if the series reader has next time-value pair.
     *
     * @return true if has next, false if not.
     */
    @SuppressWarnings("squid:S3776") // Suppress high Cognitive Complexity warning
    public boolean hasNext() throws IOException {

        if (chunkReader != null) {
            if (data != null && data.hasCurrent()) {
                return true;
            }
            while (chunkReader.hasNextSatisfiedPage()) {
                data = chunkReader.nextPageData();
                if (data != null && data.hasCurrent()) {
                    return true;
                }
            }
        }
        while (constructNextSatisfiedChunkReader()) {
            while (chunkReader.hasNextSatisfiedPage()) {
                data = chunkReader.nextPageData();
                if (data != null && data.hasCurrent()) {
                    return true;
                }
            }
        }
        return false;
    }

    private boolean constructNextSatisfiedChunkReader() throws IOException {
        while (currentChunkIndex < chunkMetadataList.size()) {
            IChunkMetadata chunkMetaData = chunkMetadataList.get(currentChunkIndex++);
            if (chunkSatisfied(chunkMetaData)) {
                initChunkReader(chunkMetaData);
                return true;
            }
        }
        return false;
    }

    private void initChunkReader(IChunkMetadata chunkMetaData) throws IOException {
        if (chunkMetaData instanceof ChunkMetadata) {
            Chunk chunk = chunkLoader.loadChunk((ChunkMetadata) chunkMetaData);
            this.chunkReader = new ChunkReader(chunk, null, currentTimestamp);
        } else {
            AlignedChunkMetadata alignedChunkMetadata = (AlignedChunkMetadata) chunkMetaData;
            Chunk timeChunk =
                    chunkLoader.loadChunk((ChunkMetadata) (alignedChunkMetadata.getTimeChunkMetadata()));
            List<Chunk> valueChunkList = new ArrayList<>();
            for (IChunkMetadata metadata : alignedChunkMetadata.getValueChunkMetadataList()) {
                valueChunkList.add(chunkLoader.loadChunk((ChunkMetadata) metadata));
            }
            this.chunkReader = new AlignedChunkReader(timeChunk, valueChunkList, null, currentTimestamp);
        }
    }

    private boolean chunkSatisfied(IChunkMetadata chunkMetaData) {
        return chunkMetaData.getEndTime() >= currentTimestamp;
    }
}
